The present invention relates generally to a system and method of focused ultrasound application and, more particularly, to a focused ultrasound system that provides precise spatial positioning under the guidance of a medical imaging system to deliver focused ultrasound to a target location.
Focused ultrasound therapy involves delivering ultrasound energy to localized regions of tissue from externally (non-invasive) or internally (minimally-invasive) located transducers. The amount of ultrasound energy delivered to tissue dictates the nature of the biologic effect produced at that location. At high intensities with continuous exposure, ultrasound energy can generate enough heat to cause irreversible thermal damage through coagulation. As the exposure is reduced in duty cycle to short pulses, the mechanical energy associated with ultrasound dominates and can be used to generate a range of bio-effects, including: vascular occlusion or hemorrhage, permeation of cells, and tissue-homogenization.
Although the concept of using focused ultrasound energy for therapeutic purposes has been known for many decades, it is desirable to develop further precise control and steering of the acoustic field in the body so as to allow for the use of focused ultrasound in a clinical setting. The integration of therapeutic ultrasound with medical imaging technologies has served to further accelerate the translation of this technology into clinical use. For example, magnetic resonance imaging (MRI)-guided focused ultrasound therapy has gained use as a non-invasive method for thermal tissue coagulation with significant promise for the potentiation of biologic therapies, local delivery of drugs, and targeted heating of tissue for enhanced drug delivery and activation. MRI enables precise targeting of structures for treatment planning, on-line temperature mapping and imaging for monitoring and control of therapy, and results in excellent visualization of the biological response to treatment. That is, an MRI system may be used to plan a focused ultrasound procedure, by performing an initial scan to locate a target tissue region and/or to plan a trajectory between an entry point and the tissue region in preparation for a procedure. Once the target tissue region has been identified, MRI may be used during the procedure, for example, to image the tissue region and/or to guide the trajectory of an external ultrasound beam to a target tissue region being treated. In addition, an MRI system may be used to monitor the temperature of the tissue region during the procedure, for example, to ensure that only the target tissue region is destroyed during an ablation procedure without damaging surrounding healthy tissue.
As the desire to use MRI-guided ultrasound therapy in clinical practice has become more widespread, a need for efficient testing in preclinical models of human disease has been recognized. Such testing commonly involves small animals such as rats and mice, which are used in biomedical research for such preclinical models. However, the small size of these animals makes focused ultrasound experiments difficult. Furthermore, large numbers of animals are required to achieve statistical significance in drug studies, requiring focused ultrasound systems capable of high throughput. To date, there is no focused ultrasound exposure system adapted for use in small animals with the capability to precisely position ultrasound energy to a target location within the animal body, as such ultrasound energy targeting may be required to be accurate within distances of, for example, 0.5 mm or less.
It would therefore be desirable to have a system and method that provides precise spatial positioning capabilities to focused ultrasound systems. It is further desired that such a precise positioning system also be useable with magnetic resonance (MR) imaging guidance to deliver focused ultrasound to a pre-determined target location.